/*
 * Copyright (c) 2003-2013, KNOPFLERFISH project
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following
 * conditions are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials
 *   provided with the distribution.
 *
 * - Neither the name of the KNOPFLERFISH project nor the names of its
 *   contributors may be used to endorse or promote products derived
 *   from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.knopflerfish.util;

import java.util.Vector;

/**
 * The <code>Queue</code> class represents a first-in-first-out (FIFO)
 * queue of objects.
 *
 * @author Per Lundgren
 */
public class Queue extends Vector<Object> {

  private static final long serialVersionUID = 1L;

  private int m_nMaxSize = -1;

  private boolean queueClosed = false;

  /**
   * Constructs an Queue with the specifies maximum size.
   *
   * @param size
   *            maximum queue size.
   */
  public Queue(int size) {
    m_nMaxSize = size;
  }

  // ==================== insert ====================
  /**
   * Inserts an item into the queue. If there are threads blocked on
   * <code>remove</code>, one of them is unblocked.
   *
   * @param item
   *            the item to be inserted.
   * @exception IndexOutOfBoundsException
   *                if maximum queue size is reached.
   */
  public synchronized void insert(Object item)
    throws IndexOutOfBoundsException {
    // Check if queue is full
    if (m_nMaxSize > 0 && size() >= m_nMaxSize)
      throw new IndexOutOfBoundsException("Queue full");

    addElement(item);
    notify();
  }

  /**
   * Inserts an item first into the queue. If there are threads
   * blocked on <code>remove</code>, one of them is unblocked.
   *
   * @param item
   *            the item to be inserted.
   */
  public synchronized void insertFirst(Object item) {
    insertElementAt(item, 0);
    notify();
  }

  /**
   * Removes and returns the first item in the queue. If the queue is
   * empty, the calling thread will block.
   *
   * @param timeout
   *            timeout in seconds.
   * @return The first item in the queue, or <code>null</code> if a
   *         timeout occurred. To distinguish timeouts,
   *         <code>null</code> items should not be inserted in the
   *         queue.
   */
  public synchronized Object removeWait(float timeout) {
    Object obj = null;

    // If queue is empty wait for object to be inserted
    if (isEmpty() && !queueClosed) {
      try {
        if (timeout > 0) {
          wait(Math.round(timeout * 1000.0f));
        } else
          wait();
      } catch (InterruptedException e) {
      }
    }

    if (queueClosed) {
      return null;
    }

    try {
      obj = firstElement();
      removeElementAt(0);
    } catch (Exception e) {
    }

    return obj;
  }

  /**
   * Removes and returns the first object in the queue. Same as {@link
   * #removeWait(float)} but this function blocks forever.
   *
   * @return The first item in the queue.
   */
  public Object remove() {
    return removeWait(0);
  }

  /**
   * Closes the queue. I.e., wakes up all threads blocking on a call to
   * {@link #remove()} or {@link #removeWait(float)}.
   */
  public synchronized void close() {
    queueClosed = true;
    notifyAll();
  }

}
